have you been to baltimore? this is not the dirtiest city. >> she's right. baltimore ranks third but san francisco deserves to be on the list too, according to some tourists, like this family from australia. >> yeah, it has been a little grimy and dirty. my son got spit on. >> the counterpoint to the not so pristine conditions, the magazine gave san francisco high marks for fine diving, ethnic food, tech savvy people and good transportation. >> those things really overpower the fact of the dirtiness. i think the fact of the matter is most visitors in cities in the united states rank higher than we are. >> mayor ed lee said it's time for a spring cleaning campaign. >> i think everybody will agree, there are our favorite corridors that we always like more people to see, but we don't like the trash on the streets or illegal dumping or graffiti. >> and the mayor really knows, he used to be the head of the department of public works in charge of cleaning up all that stuff. by the way, this survey was taken from may through august of last year, but the results wer